Help! My Backyard is Sinking!

I have ignored it because summer usually brings it back...but this year...well, this year is different.

I live in Falmouth and have been told that the land under my home and in the whole neighborhood is clay when you dig deep. With clay, water doesn't get soaked into the ground. It just sits there.

The dark area is standing water that has been there since...well, it was ice before. It's been a long time since you haven't sloshed and sunk.

Some of it is the heaving ground from ice and warmth...but some of it is plain sinking. I was thinking that maybe I just need a bunch of dirt...land fill.

This is the foundation of the shed. It used to sit in the dirt...and the dirt has gone away!

This used to be a nice little garden with a nice little border...uh, not so much.

Okay...I am not an expert. Does anyone know what I should do? And should I plan on robbing a bank to pay for it?